In any forward traveling wave tube amplifier device, a beam of electrons gives up energy to a high frequency RF signal to amplify the signal. The RF signal is propagated by a slow-wave structure with a phase velocity that is a fraction of the free space velocity of the RF. The beam of electrons is propelled into the region of the slow RF wave, in the same direction as the propagation direction of the slow RF wave, and at essentially the same speed. Before entering the region of the slow RF wave, the electron beam is accelerated by the electron gun to the slow-wave phase velocity. The electron beam and the slow-wave interact in that region. During interaction between the beam electrons and the propagated slow-wave, interacting electrons are velocity-modulated causing bunching of electrons along the transiting beam and a general slowing of the beam. To maintain synchronism of electron beam and slow-wave through the interaction region, the slow-wave circuit is designed for slowing progress of the slow-wave along the interaction region. When operating conditions are proper there is maximum transfer of energy from the electron beam to the RF signal. The conducted signal is amplified and gain is related to the length of the interaction region in wavelengths and to the current density of the electron beam that interacts with the propagated slow-wave.
U.S. Pat. No. 3,781,702 issued to Louis J. Jasper, Jr., coinventor in this application, discloses a traveling wave tube that includes an electron gun supported between and coaxial with parallel ceramic disks that are sealed at their perimeters to a conductor ring coaxial with the electron gun. A slow-wave circuit, in the form of a conductor spiral, is printed on an inner surface of one or both of the disks. The amplifier operates wide band. There is need for traveling wave amplifiers for use in expendable jammers or other expendable high frequency electronic equipments. Such expendable single-use amplifiers should be low cost and of comparatively simple structure. For use in a missile, it is necessary to restrict weight and size. Therefore, there is need for a traveling wave amplifier that is as lightweight and compact as possible. For compatibility with battery power available in expendable equipments, the amplifier should be operable at low voltage, and be low power, and efficient. Also there is need for improved modulator and amplifier devices for use in place on phased array antenna assemblies. Additionally, consumer items such as microwave ovens need lower-voltage, higher-current, more economical traveling-wave amplifiers.